Nicotine polacrilex (chewing gum) has been under investigation as a replacement for tobacco-delivered nicotine and also as a convenient drug administration modality which provides a model of more general interest for drug dependence researchers. For example, nicotine gum was employed in our initial studies to examine the capabilities of this Laboratory's recently established performance and electrophysiologic assessment approaches for evaluating drug effects. The course of research conducted using this preparation has been determined by the priorities of the ARC and the Chief of the Biology of Dependence Laboratory. These studies have included the following: (1) Effects of nicotine gum replacement on cigarette smoking and tobacco smoke exposure; (2) Pharmacodynamic effects of nicotine gum compared to other routes of nicotine administration; (3) Abuse liability of nicotine gum; (4) Dose-related effects on subjective, behavioral, and physiologi variables, including studies of the factors which may affect the functional dose, such as chewing and swallowing rates; (5) Effects of nicotine gum administration on learning and performance in non-smokers; and (6) Role of oral pH in nicotine absorption.